Closures



Nov. 22, 1960 COOKE AL 2,961,110

CLOSURES Filed May 14, 1957 FIG.].

FIG. 2. J

INVENTORS GILES B. COOKE WILLIAM C. RAINER ATTORNEYS United States Patent CLOSURES Giles B. Cooke and William C. Rainer, Baltimore, Md.,

assignors to Crown Cork & Seal Company, Inc., Baltimore, Md., a corporation of New York Filed May 14, 1957, Ser. N 659,149

'3 Claims. (Cl. 215-39) This application is a continuation-in-part of application Serial No. 400,746, filed December 28, 1953, now Patent No. 2,796,189, issued July 18, 1957.

The present invention relates to closures and, more particularly, metal closures of the screw, lug, pressed-on and crown types, as well as the use of novel stamping lubricants in the preparation of such closures.

An object of the invention is to produce decorated or plain coated metal closures or metal closures without any coating, which will be resistant to scratching, which will be protected against moisture, which will have a more attractive luster and sheen and which will feed more easily in the hoppers of capping machines.

In addition, the present invention aims to reduce substantially the dusting which develops when metal caps are fed in a cap machine and occasioned by the abrasion of the caps with each other and further to reduce the dusting which occurs in the cartons in which the caps are shipped where there is frequent abrasion of the caps with each other and in which the sharp edges of the crown skirts have a tendency to abrade and scratch the decoration on the caps.

Moreover, it is an object of the invention to provide metal closures which will be free of a characteristic attribute of closures having an oil or wax coating, namely, of picking up dust and foreign matter so that in accordance with the present invention, the caps are maintained clean, which is important, particularly where such closures are utilized in the packaging of foods, beverages and pharmaceuticals.

It is a further object of the invention to preclude the sticking which sometimes develops when metal closures are stacked in nested relation for feeding in a capping machine. Where this sticking occurs in the stack, the high speed feeding operation must be stopped and the caps individually separated in order that proper feeding may be resumed.

Yet another object is to improve the stamping operation in forming metal closures.

In producing caps or closures in accordance with this invention, the stamping out of metal shells is a very important step, and it is an object of the invention to assure that the decorated sheets will be in a condition to allow the cap shells to be stamped therefrom accurately within precision tolerances and without marn'ng or scratching the coating or decorated surface.

Still further objects and the entire scope of applicability of the present invention will become apparent from the detailed description; it should be understood, however, that the detailed description and specific examples, while indicating the preferred embodiments of the invention, are given by way of illustration only since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

In the drawings:

Figure l is a side elevation of the stamping die in position to cut a closure blank from a metal sheet;

ice

Figure 2 is a perspective view of the metal closure disc;

Figure 3 is a vertical section of a finished closure;

Figure 4 is a vertical section of the stamping die; and

Figure 5 is a fragmentary vertical section of a glass container having a screw cap with a rubber ring sealing liner.

Referring more specifically to the drawings, there is provided the customary plain vinyl lacquer (vinyl acetate-vinyl chloride resin) coated metal tinplate (steel) sheet 2 which is provided with a thin film 4 of a silicone, more specifically, General Electric Companys SM61 or Dow Cornings DC 200 (methtyl polysiloxane). The silicone is applied to the metal sheet by spraying thereon. Alternatively, the silicone may be spread, roller coated, brushed or wiped on. After the silicone is applied to the sheet, the latter then passes to the stamping die 6 which simultaneously cuts out and shapes closure blank 8. Instead of applying the silicone resin to the sheet, it can alternatively be applied to the stamping die 6. This form of the invention is illustrated in Figure 4 wherein the inner shaping surface 10 of the die 6 has a thin coating 12 of silicone applied thereto.

A finished crown closure is illustrated in Figure 3 wherein the closure 14 has a conventional metal top portion 16 and fluted skirt 18. The outer surface of both the top 16 and skirt 18 has a thin methyl polysiloxane film coating 20 resulting from the stamping operation. The closure includes a sealing gasket 22 which is made of cork. Alternatively, the sealing gasket can be made of a plastisol, e.g., a vinyl chloride resin plastisol comprising 64 parts of vinyl chloride resin and 36 parts of a plastisol forming plasticizer such as dioctyl phthalate.

The sealing gasket can also be formed of cork and have a plastic, e.g., polyethylene, facing. When screw and lug caps are employed, the gasket can be made of rubber or treated papers such as is conventional in the art.

Referring more specifically to Figure 5 of the drawings, there is shown a glass container 24 having a threaded top 26 sealed by a closure 28. This closure comprises a metal shell 30 having a top 32 and an internally threaded skirt 34 depending therefrom. The interior surface 36 of the top of the shell is provided with a relatively flat cushion liner 38 for engaging in sealing relation the sealing lip of the container to seal the same. The exposed surface 40 of the cushion liner which engages the container sealing lip has a coating 42 comprising a thin film of liquid polysiloxane.

The use of silicones protects the organic coatings during the formation of the threads, lugs and knurls of closures of the screw and lug type, for example. The silicones also protect the decorated surface and the interior of these caps. This is an important advantage of the invention, for example, when utilized with beer crowns and screw and lug caps which are used on certain food products which are later subjected to pasteurization or sterilization.

The silicones or siloxanes which can be used in the persent invention include the methyl polysiloxanes having the following formula:

and which remain fluid at room temperature even though n may vary from 0 to 2000 or more. Specifically, n can be 0, 15, 50, 200, 500, 1000, or 2000.

While preferably the siloxane used is a methyl polysiloxane, the methyl radical in the formula can be replaced by other organic radicals, such as monovalent hydrocarbon radicals including aryl radicals such as the age length of the molecular chain determines the viscosityof the fluid. The coating comprises a dispersion of the polysiioxane in water or some volatile organic vehicle', for example, isopropyl alcohol. Any organic solvent should be one which will be inert, i.e., will not soften the coating on the metal and should be readily removable by volatilizingv at a temperature below any'used in halo ing the organic coating.

The water dispersion employed usually comprises from.

about 1% to about 5% of the silicone. In applying-the silicone to the metal sheet of Figure l, a 2% solution of Dow Cornings -DC 200 (methyl polysiloxane) V was sprayed onto the sheet.

It is sometimes preferable to use more concentrated silicone dispersions, e.g., a 36% aqueous silicone disper- Unless otherwise indicated, all percentages and proportions in the specification and claims are by weight.

The aqueous silicone coating 'is applied to the surface of the metal sheet or the stamping die by conventional coating techniques, such as spraying, brushing, wiping or with the aid of a roller, etc.

The silicone can be coated on one or both surfaces of the metal sheet. Following the provision of the silicone coating on one or both surfaces of the sheet, the vehicle, e.g., water or the organic vehicle, is volatilized in any suitable manner, e.g., with heat or by means of a current of air. This air may be dry in some cases, and also may be warmed or heated to as high as 240 F., the latter to assure speedy removal of the vehicle. In certain cases, it may be desirable to apply a film of silicone from the pure polysiloxane without solvent. The siloxane is deposited upon the decorated or plain coated surface of the metal sheet as a thin protective coating, which is susbtantially continuous and is resistant to moisture. This facilitatesithe movement'of the sheets over each other as they are automatically fed into the stamping press, reducing scratches and maintaining a clean, brilliant, and continuous coating or decoration. At the same time, this coating exerts a lubricating action with respect to the stamping dies for punching out the cap shells, as a result of which the cap shells are accurately formed and the caps are free of abrasion or scratching while the stamping apparatus itself is lubricated and thereby protected from wear so thatit operates in a true manner for an augmented period of time.

The cap shells having a plain coating or a decorated coating thus produced are provided with an outer exposed coatingof the polysiloxane whichhas a number of advantages, as above related. For instance, the shells do not stick to one another .as, for example, in the case of caps which are stacked in nested relation. Furthermore, the surfaces of the caps are abrasion resistant, so that the decoration or finish is not marred and the caps will also present an attractive appearance. Again, the caps, by reason of their siloxane coating, feed readily in the capping machines which, in high speed capping apparatus, is of great significance. In this connection, flee siloxanecoating is of extreme thinness, while giving maximum protection, and by reason of its thinness, the full effect of the decoration is preserved and presented which would not be true where customary protective lubricants are utilized which have to be employed in substantial thickness to afford the desired protective results, as well as the lubricating action. In connection with the decorated metal plates, as well .asthe caps stamped therefrom, the surfaces are of such a character that they do not pick up dust or dirt or foreign matter. The advantage of this can be readily appreciated, particularly when the caps are to be employed in connection with food products, beverages or pharmaceuticals. Of considerable importance is the fact that dusting, occasioned by abrasion, is substantially reduced in the hoppers of the capping machines, as well as in the shipping cartons. It is also interesting to note that the presence of the siloxane coating protects the metal plate from which the caps are stamped as well as the caps themselves as, for instance, where there are any spots of metal which are exposed or which have become exposed by reason of the fabrication of the caps from the metal plate. That is to say, if the die should scrape off spots of the decorated or plain coating the siloxane coating creeps and seals up spots and, in addi tion, the die itself Wipes the siloxane coating over said;

spots to form a protective coating on the same.

It will thus be seen that the presence of the siloxane coating has tremendousadvantages in enabling the stamping of the caps from the decorated metal sheets and also the presence of the siloxane is highly advantageous in the finished caps which have been stamped from such sheets.

As previously indicated, the silicone lubricant can be used in various concentrations, e.g., 1%, 5%, 20% and 36% Water dispersions having proved satisfactory. An

aqueous dispersion of 2% silicone has proven satisfactory for lubricating decoratedsheet metal which is stamped into screw and lug caps.

For some purposes, it is desirable. to disperse the silicone in an organic solvent. As an example, isopropyl alcohol may be used. The concentrations are the same as in the use of water dispersions. It' is important, however, that the organic solvents selected have no deteriorating effect on the decoration or coating. In all cases, for caps and closures which are used in the food and beverage industry sanitary grades of silicone DC 200 or SM61 are employed. The coatings are applied at room temperature in a manner similar to the conventional waxes and lubricants.

Where residual water is objectionable because of a. deteriorating efiect on the machine dies, the coated sheets may be dried in warm air or by any other suitable means. Likewise, in some cases, it may be desirable to air dry sheets which have been lubricated with silicone in an organic vehicle. This drying would remove all traces of the organic solvent so as to prevent any softening or deterioration of the coating or decoration.

In some instances, it is found desirable to use silicone. When this is done, it is important for reasons of appearance, as Well as economy, that the coating equipment be precision controlled so that only a veryminute film of the silicone is applied to the surface of the metal.

In some cases, it is also desirableto have the silicone lubricant applied to the stamping dies. When the dies are coated with a film of silicone, abrasion to the coating or decoration during the stamping is even further reduced or eliminated. In normal operations, some silicone lubricant will build up on the dies and only in special cases would it be necessary to apply the silicone directly to the parts of the dies.

We claim:

1. A metal cap having a cap shell coated with a thin film of a liquid polysiloxane.

2. A metal cap according to claim 1 wherein the polysiloxane isa methyl polysiloxane.

3. A metal crown closure shell having the top portion coated with a thin film of a liquid polysiloxane.

References Cited in the file of this patentv UNITED STATES PATENTS 1,974,981 Carvalho Sept. 25, 1934 2,120,461 Copeman June 14, 1938 2,690,255 Kaiser et al Sept. 28, 1954 2,697,532 Hutafi Dec. 21, 1954 2,706,572 Tocco Apr. 19, 1955 2,768,906 James Oct. 30, 1956 FOREIGN PATENTS 508,732 Canada lan..4, 1955 

